Motorists who travel on a major new road mooted for Auckland will be hit with a triple whammy in the form of fuel excise, regional fuel tax and tolls, National says.

Transport Minister Phil Twyford has said the Penlink route, one of two new road projects to be announced today with Auckland Mayor Phil Goff, would be done under a private-public partnership.

To make it attractive to investors, it would be a tolled road.

"Because of the design of the road it's easily tolled. That generates a revenue stream that gets the project over the line. Without that it probably wouldn't get over the line," Twyford told RNZ.

Although the numbers hadn't yet been crunched on how much motorists would be charged, Twyford estimated it would be around $2 or more per trip.

National's transport spokesman Jami-Lee Ross said that would deliver a triple whammy for motorists using the route.

"If you're a Rodney resident and you want to use that road, you're paying a toll, you're paying more in fuel excise and you're paying more in a regional fuel tax."

It should be noted that the Rodney Local Board has also proposed an average transport tax rate hike of 7.3 per cent for ratepayers.

Ross said the wider announcement today, which will include plans for light rail, would mean many Aucklanders would be contributing financially to something that would not ease their transport woes.

"We're going to see that light rail will be funded for Dominion Rd. We're not going to see much in the way of new projects for other parts of Auckland.

"You're going to see people on the North Shore, people in east Auckland, people in west Auckland effectively paying more in petrol taxes, they're going to be paying a regional fuel tax on top. They're not going to be seeing much in the way of improvements but they're already subsidising trams down Dominion Rd. I can't see that Aucklanders will want to see that happening," Ross said.

Auckland Council is expected to introduce about 10 cents a litre in regional fuel taxes to pay for its share of major transport projects and the Government's new 10-year policy plan for transport proposes a further nationwide fuel excise increase of 9-12 cents litre over three to four years.

Penlink will provide a new connection between Whangaparaoa Peninsula and the Northern Motorway. The other is Mill Rd in the south, improving the connection from Manukau through Takanini to Drury.

The announcement will be part of a new 10-year funding package for Auckland transport.